Angular 4:何时以及为什么在构造函数中使用@Inject? [英] Angular 4: When and why is @Inject is used in constructor?

问题描述

问题陈述

我正在学习 Angular 4，我偶然发现了一个代码，其中 @Inject 被用于 constructor 并且我无法弄清楚为什么......

I am learning Angular 4 and I have stumble upon a code where @Inject is being used in a constructor and I am not able to figure out why...

代码和源代码

我使用的是 Angular 4 材质

I am using Angular 4 Material

代码来源: https://material.angular.io/组件/对话框/概览

在代码中，他们注入了MAT_DIALOG_DATA

constructor(public dialogRef: MatDialogRef<DialogOverviewExampleDialog>,
             @Inject(MAT_DIALOG_DATA) public data: any
           ) { }

谁能详细说明这是什么意思，我们应该在何时/何地执行此操作?

Can anyone please elaborate what does it mean and when/where should we do this?

推荐答案

@Inject() 是一种手动机制，用于让 Angular 知道参数必须被注入.

@Inject() is a manual mechanism for letting Angular know that a parameter must be injected.

import { Component, Inject } from '@angular/core';
import { ChatWidget } from '../components/chat-widget';

@Component({
  selector: 'app-root',
  template: `Encryption: {{ encryption }}`
})
export class AppComponent {
  encryption = this.chatWidget.chatSocket.encryption;

  constructor(@Inject(ChatWidget) private chatWidget) { }
}

在上面我们要求 chatWidget 成为单例 Angular通过调用与 class 符号 ChatWidget 关联@Inject(ChatWidget).重要的是要注意我们正在使用ChatWidget 用于其类型和作为其单例的引用.我们不使用 ChatWidget 来实例化任何东西，Angular 会为我们在幕后

In the above we've asked for chatWidget to be the singleton Angular associates with the class symbol ChatWidget by calling @Inject(ChatWidget). It's important to note that we're using ChatWidget for its typings and as a reference to its singleton. We are not using ChatWidget to instantiate anything, Angular does that for us behind the scenes

来自 https://angular-2-training-book.rangle.io/handout/di/angular2/inject_and_injectable.html

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